Linux view port usage status, close port method (netstat, lsof)

In some projects, there are requirements for network layer security, and only necessary network ports are allowed to be opened, so R&D is required to know the specific role of each open port.

 

The following content is reproduced from other articles and is only a summary:

Everyone knows that the port does not exist independently, it is dependent on the process. When a process is opened, then its corresponding port is opened, and when the process is closed, the port is also closed. If a certain process is opened again next time, the corresponding port will be opened again. Don't just understand it as shutting down a port, but you can disable a port.

 

View port:

netstat -antp

busybox netstat -antp

注：加t参数，可以使之打印端口对应的进程

Another way to view the port corresponding process:

lsof -i:xxx

注：lsof是一个单独命令
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相关文档：https://blog.csdn.net/weixin_33857230/article/details/92130771

Close port

There are two ways to close the port: disable the port/kill the corresponding process

        【iptable】
        sudo iptables -A INPUT -p tcp --dport $PORT -j DROP"
        sudo iptables -A OUTPUT -p tcp --dport $PORT -j DROP"   

        【kill】

        kill -9 PID" (PID：进程号)